Moisture indicator



July 30, 1935. R. BROWN ET AL 2,009,760

MOISTURE INDICATOR Filed Jan. l0, 1929 2 Sheets-Sheet@ z'r Coo er' ir Cooler July 30, 1935. R. BROWN Er AL MQISTURE INDICATOR Filed Jan. 10, 1929 2 Sheets-Sheet 2 J7 710 g@ J7 '5C-ILV Nm JL -fz 12, Z2 A efllfaance. 22

27 Jal/'feb 2LT Jfies Pea., 2 gef? 60'7- Z 23 C 'l 7l [caf/)1y amp 17.10 i "'DL NIJ 75... j W @ah/7' Patented July 30, 1935 MOISTURE INDICATOR Richard Brown, Auburndale, and Edwin H. Perry, Worcester, Mass.

Application January 10, 1929, Serial No. 331,585

1 Claim.

. This. invention relates to an apparatus for indicating danger `of short circuiting due to the accumulation of moisture in a generator supplied with a surface air cooler,or'washer, and is an 5j improvement over that shown in our abandoned application,.Seria1'No. 711,031, led May 5, 1924. The principal object of the present invention is to provide means, whereby the indicator can be dried out by the current passing through ity without danger. The invention also involves improvements in the arrangement ofthe parts to keep the current on for a period to insure the drying out of the indicator until no current will V, iiow through it. y Y

" Reference -is toV be had to drawings, in which ;Fig. 1 is a central, vertical, sectional view of a large alternator provided with a surface air cooler to which this invention is particularly adapted;

Fig. 2 is a side view of the indicator itself;

Fig. 3 is a wiring diagram showing how it may be dried out automatically;

Fig. 4 is a similar view of almodication in which the drying action is not automatic, and

Fig. 5 is a similar view of `a modiiication for an alternating current.

1 The-invention is shownas applied to lan alternator in Fig. 1. We shall not describe the alternator, but the drawings are lettered to show the different parts.

The fans direct currents of air inwardly down through the center, as indicated by the dotted lines, throughthe air coolers which are provided `with pipes for conducting cold water through them. The air is cooled and drawn up at the ends around the shaft back'through the machine to cool thesame. This is the ordinary construction. Short circuiting will result if .much mois- 40- ture gets into these air currents.

-We"locate a pair of moisture vindicators at pointsV in the currents of 'air just described.

the accompanying 'I'hese indicators are so located, therefore, that' the moisture in the air affects them lbefore it can 451V' enter the machine and, as the moisture increases,

the" indicators will: eventually give the` signal before any danger point is'reached Each lindicator comprises a brass pipe I0 constitutingl a conductor mounted on brackets II supported by the beams or in any other convenient way. This brass pipe is covered by a continuous layer IB of porous material, as asbestos bre and the end of the pipe is connected by a wire I2 to a source of power. The other terminal is connected with a conductor in the form of a coil of wire I5 wound on said layer of asbestos I6 with which the pipe I0 is covered. The coil of wire I5` is a single coil with the coils spaced apart,A preferably, extending along the pipe to any de- -fi sired distance but not, of course, capable of com- 5` inginto contact with the pipe anywhere. We have also shown the ends of the pipe I0 as provided With bre insulators I1 so that there is no danger of the pipe I0 coming into contact with supporting brackets at either end. We also pref- 10 erably wind layers of cotton tape I8 on the outside of the coil I5 so as to protect the asbestos.

When the asbestos is moistened by the'presence of air having or more relative humidity it will vallow a current to ilow through the circuit, 15 that being the only insulator in the way. Its insulating properties are neutralized by the moisture. We have discovered that this absorption element will stand all the current it will take when connected electrically, when either direct 20 or alternating currents are employed, whether thel asbestos is soaking wet or any degreeof wetness between soaking wet and bone dry. Further it becomes dried out by virtue of the current flowing through it due to its wetness and if 25 allowed to dry it will become so thoroughly dried out that no further appreciable current will flow through it. We speak now of a source of current maintained at volts or thereabouts. In Fig. 3 we have shown a diagram based on 30 the above principle for the purpose of carrying it out for the purpose of drying the asbestos without danger, blowing the horn I3 or other alarm device, and operating the pilot lamps 2U at the proper time. The source of power is indicated by 35 the plus and minus signs. One main goes directly to the collar which is connected withv the wire I5. The other one is connected with the pipe IG through a shunt relay coil 2| and a current limiting resistance 22 `and wire I2 which f10 has been mentioned. This resistance 22 may be used for the purpose of preventing a sudden ilow of high current under peculiar conditions, which do'not occur frequently. This coil 2l, whenthe current is flowing, is arranged to operate a pair 45" of contacts 23 from a neutral position or a position" in 'contact with a pair of contacts 24 toa position in which they engage a pair of contacts 2 5. In the latter case the current is divided and part of `it goes through the series relay coil 26 50 to the 'other side of the une. Part of this current in this case goes from the plus side through the signal I3, contacts 25 and 23 and right across to the minus side. When the asbestos dries out so the current cannot ow through the coil 2|, 55

the contacts 23 will drop and there will be only a small current through the coil 26, of course. Neither will there be much through the horn I3 but there will be a current from the plus side of the line to the pilot lamps 20, contacts 24 and 23 to the minus side of the line. The coil 26 serves as a parallel path to the coil 2| and provides a stick circuit for the contacts 23 so that the relay may be kept energized by a smaller current than was required orginally'to sound the alarm. This increases'v the conductance vand therefore' increases the drying current. The current owing through the coil 26 then draws the contacts 23y back into engagement with the contacts 25. Y

In this way the moisture indicating element is in combination with an electric circuit comprising a switch or relay or both so that the element will be connected directly across the source of power automatically when it is wet in order to dry it out. At that time the signal will be given and the pilot lamps will go out, but when the device is in the proper working order the pilot lamps will go on again, showing that the unit is normal and ready to act again.

This can be made to be operated manually as shown in Fig. 4 and the coil 2l will operate 'the contacts 23 in the same way as before but in this case a switch or push button 2l will have to' be closed to out out the coil 2l and dim the indicating lamp 28 to more quickly dry the asbestos.

The same results can be made in an alternating current system, and we have shown a diagram for that in Fig 5 in which most o the parts are the same and the coil 2l operates the contacts 23 in the same way. A transformer or relay or both fthe lamp 28 to close the contacts 25 and affect a v'oltmeter or ammeter or other instrument, as

may be desired. Upon increasing wetness induction will cause an increase of current to flow, due to the saturation of the iron magnetic circuit which current will dry out the element automatically.

In any of these cases the asbestos insulating material will conduct a current when it is suiliciently Wet and will be dried out without danger of injuring it. As a matter of fact we have found that the use of cloth or paper of any kind in place'of the asbestos covering is all right for operation of the device once but it cannot be dried out by any means that we have been able to discover Without puncturing it or injuring it to such an extent that it cannot be depended upon to 4work again.

The operation of the device is very simple. Normally with no moisture present current ows from minus through coils 2| and 26, signal I3 to plus, but this current due to the resistance of this path is of insuicient value to operate the signal device and to lift the armature 23; also` current iiows from minus through contacts 24 and bridge 23 through the pilot lamps and to plus, thus operating the pilot lamps; when moisture occurs current ows through from plus to wire I5, asbestos, rod I0,`resistance 22, coil 2| to minus, this current being of such strength as to lift armature` 23 and bridge the contacts 25 connecting the signal device I3 directly across the line and the coil 26 is connected in parallel with the coil 2 I; under this condition more current ows than before and the asbestos is dried more quickly; when the asbestos is dried out the current flow through the coils is cut down to its original value and the armature 23 is dropped into engagement with the contacts 24. This will illuminate or sound the signal, as the case may be, and the operator can then stop the machine before any danger is done. This is a very'simple,inexpensive and effective way of ensuring the machine against short circuiting from this cause.

The asbestos will be dried out automatically in the form shown in Figs. 3 and 5 and by simply pressing the button in the form shown in Fig. 4 with either alternating or direct current. When dried out the current will stop flowing and the parts will return to their normal safe position and indicate by their lights 20 that everything is in working order and that there is no danger to the generator-from moisture in the coils. the device is readyto work over and over as many times as may be required.

Although Vwe have illustrated and described? only three forms of the invention and shown' it as appliedto only one form of electric machine,.

we are aware of the fact that other modifications can be made therein by any person skilled in the art, and that it can-be applied toother generators or machines without departing from the scope' of the invention as expressed inA the claim. There fore, we do not wish to be limitedl to all the d'etails of construction herein shown and described, but what we do claim is:-

The combination of two conductors located in a path of air currents, a continuous, layer of absorbent asbestos bre llingthe ,space between the conductors, wherebyV when the asbestos is moistened a path for a current of electricity will be established through it from one conductor to the other and the asbestos will be dried out thereby, a source of electric current, one conductor being connected to one terminal of said source', a shunt relay coil and a series relay coil, one terminal of each coil being connected to the other conductor, a pair of separated front contacts, one of said contacts being connected to the other terminal of said shunt coil and to the other terminal of said source of current, the other contact being connected to the other terminal of said series coil and to one terminal of a signal device, the other terminal of the signal device being connected to said rst terminal of said source of curi rent, a pair of separated back contacts vfor said coils, one of said back contacts connected to said other terminal of said source and the other back contact being connected to one terminal of a pilot lamp, the other terminal of which is connected to said rst terminal of saidsource of current, a. bridging contact member for said pairs of contacts, means movably mounting said bridging member so that it engages said front pair of contacts when the shunt coil is energizedv due to a wet condition of the asbestos, and the back pair of contacts vwhen the asbestos is` dry, the current passing through the coils and signal device in the latter condition being" of 'insuicient value to lift the bridging member' and to operate the signal due to the selected resistance of thev elements.

RICHARD' BROWN- EDWIN H. PERRY. 

